The present invention relates to a connecting spring. Such spring is used, for example, in a connection terminal to connect an electrical conductor.
It is known to use springs for holding the end of a stripped conductor against a current supply rail, in a connection terminal. Documents DE-37 27 091 and DE-42 37 733 describe connection terminals of this type. These documents disclose a connecting spring made of a flat elastic material bent into a loop. The connecting spring has a pressing branch intended to rest against a connecting strip or a current supply rail, a gripping branch folded from the rear part of the connecting spring and running transversely to the connecting strip, and an elastic arc connecting together the pressing branch and the rear part from behind. A window intended to accommodate an end of a stripped conductor and the end of the connecting strip is made in the gripping branch. The stripped end of a conductor is laid along the connecting strip on the opposite side to the pressing branch of the spring. Thus, the spring presses this stripped end against the conducting strip.
A device of this type may also be used for making a self-stripping connection of an electrical cable. In this case, the spring is used to store up the energy needed to strip the insulation off an electrical cable and trap it in a connecting slit and to restore this energy at the appropriate time.
These connecting springs have to guarantee a pressing force exerted on the stripped conductor toward the connecting strip so as to obtain a good contact pressure and thereby a good electrical connection. These relatively high forces lead to high internal stresses, particularly when the spring is stressed. These stresses appear more particularly in the elastic arc.
In order to keep these stresses at a level that is compatible with the properties of the material, the size of the spring has to be increased and this leads to an increase in the bulk and cost of the connection.
It is an object of the invention therefore to provide a connecting spring in which the stresses are reduced by comparison with a connecting spring of the prior art, without increasing the bulk.
To this end, the invention proposes a connecting spring for an electrical conductor, made of a flat elastic material which has a pressing branch intended to rest against a fixed conducting strip of a connection terminal, a moving branch, having, on the one hand, on a same side of its free end, a more or less flat part with an opening intended for the passage of the end of a conductor that is to be connected and, on the other hand, a rear part facing the pressing branch, and a connecting region connecting the two branches, forming a loop.
According to the invention, the pressing branch has an elbow toward the inside of the loop so that when the pressing branch is pressed against the flat conducting strip, the distance separating the inside of the elbow from the conducting strip is greater than the thickness of the material used to make the spring.
Thus, the pressing branch rests via its two ends on the conducting strip. When the connecting spring is deformed, the two contact points tend to move apart by sliding along the strip, tus opening out the elbow in the pressing branch. This deformation allows some of the stresses needed for stressing the spring to be stored up. The appearance of stresses in the pressing branch makes it possible to reduce the stresses in the connecting region. It is in the latter that the stresses are the highest. The bent shape of the pressing branch thus allows for better distribution of the stresses.
In a preferred embodiment, when the pressing branch is pressed against the flat conducting strip, the distance separating the inside of the elbow from the conducting strip is between two and four times the thickness of the material used to make the spring.
In a connecting spring according to the invention, the part of the spring may, for example, be more or less straight.